In this second book of Doyle's Dublin trilogy (i, ON and End.), black and white giants stride through the images, stalking Dublin streetscapes. The figures, the buildings, the sky — even the light itself — all seem to be rendered from the same mass of concrete.

ON was published with three different covers — red, green and blue — with alternating foil colours and finishes. The colours of the covers flood across the pages at three points in each of the the books. ON has no end-papers, the tritone images start as soon as you open the book, and end as abruptly. There is no text, apart from the publication details on the spine.